The present invention relates to optical data disks such as compact disks, and more particularly to devices for protecting disks from damage by scratching and the like, that can be applied by users of the disks.
Data disks such as compact disks and video disks typically have large amounts of digitally stored information that is optically readable through a transparent bottom layer of the disk by a movable head during rotation of the disk. The information is arranged in one or more tracks that are covered by a thin protective top layer of the disk that can have labeling applied thereto such as by silkscreening. Normal handling of the disk can result in scratching of the bottom layer, resulting in loss of data by interference with the optical path such as by loss of focus and/or lateral image displacement. Also, data can be lost by scratching of the protective layer which is typically very thin, on the order of 20 microns, resulting in removal of information from a vapor deposited metal layer that is only about 0.1 micron thick. Even the loss of a small portion of the information can be catastrophic in that normal reading of information past a damaged portion is blocked in many systems. U.S. Pat. No. 4,983,437 to Merrick discloses a compact disk protector in the form of a polymer disk having a self-adhesive backing for application onto the protective layer of the data disk. The protective disk can be transparent for viewing the labeling, or it can have other indicia applied thereto. A disadvantage of the disk protector of Merrick is that it is unsuitable for protecting the bottom disk layer, in that optical transmission through the adhesive backing is ineffective, being excessively attenuated and irregular. Also, the protector is not readily replaceable in that the protective layer is subject to failure during attempted peeling of the protector, and residual adhesive that is likely to be left behind is objectionable.
Thus there is a need for a disk protector that overcomes the disadvantages of the prior art.